The background description provided here is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Substrate processing systems may be used to etch film on a substrate such as a semiconductor wafer. The substrate processing systems typically include a processing chamber, a gas distribution device and a substrate support. During processing, the substrate is arranged on the substrate support. Different gas mixtures may be introduced into the processing chamber and radio frequency (RF) plasma may be used to activate chemical reactions.
Referring now to FIG. 1, when integrating some semiconductor substrates such as vertical NAND devices, silicon nitride needs to be etched with very high selectivity to other exposed materials. Hot phosphoric acid is the main chemistry that is used for etching silicon nitride film in these devices. This etch process has several limitations that need to be addressed including the ability to scale above 36 layers, reducing defects and pitting, and improving control of the etch rate. For example in FIG. 1, a single defect particle 10 may cause loss of a write line string in a memory device 14.